1. Field of the Invention
This invention relates to devices and methods for testing tires for flaws. More particularly, this invention relates to a high voltage device and method for testing for flaws in a tire.
2. Background Information
Visual inspection and testing of tires is a common practice in the tire retread business. Testing of used tires for flaws, such as gashes, holes, and nails and other foreign objects, is a common practice. After detection, the nails or other objects may be removed and/or the tire may be patched in order to repair the tire. Although visual inspection may be used to detect some flaws, other flaws may not be visible to the human eye or may not be detected by visual inspection due to human error.
Some devices do exist for the detection of flaws in tires. For example, some machines may inflate the tire and then detect flaws either ultrasonically or by observing bubbles that indicate escaping air. Such machines, however, have the disadvantage of requiring inflation of the tire to be tested.
Other devices use high voltage to detect flaws in tires. See U.S. Pat. No. 4,520,307 ('307 patent), issued to Weiss on May 28, 1985. The '307 patent describes a high voltage inspection system in which a high voltage head 4 is mounted within the tire. A tire spreader (with arms 22) is used to spread the beads of the tire apart and the high voltage head 4 is then mounted within the tire. '307 patent, FIG. 4; Col. 5, ll. 20-28, 44-48. A rotating drive mechanism 16 with drive rollers 18 and 20 is then used to rotate the tire. '307 patent, FIG. 4; Col. 4, ll. 65 to Col. 5, ll. 3. Upon detection of a flaw, an arc-over develops as current flows through the head 4 to a reference head on the other side of the tire, which may be the rollers 18, 20. '307 patent, Col. 5, ll. 65 to Col. 6, ll. 4. The operator may then stop the rotation of the tire and mark the flaw with a pen or crayon so it may be fixed at a later time.
The device of the '307 patent requires the use of a "suitable mechanical linkage 25" to position the head 4 within the tire. '307 patent, Col. 5, ll. 44-48. Tire testing devices developed in accordance with the teachings of the '307 patent may have somewhat complex mounting arms for the head because positioning of the head 4 within the tire is important for a number of reasons. The head must be sized to be small enough to fit within the beads of the tire when spread, and yet the head should be large enough to create an electric field over the desired surface of the tire to be tested. Pins or small chains may be used to carry an electric charge on the head and, in that case, the pins should cover the surface area of the tire to be tested. Alignment of the head within the tire becomes key so that the pins are properly spaced throughout the inside of the tire.
Pneumatic and mechanical arms are commonly used as a mechanical link to mount the head within the tire during testing. Such pneumatic and mechanical arms typically allow for the head to be moved vertically as well as horizontally. Using such a pneumatic and/or mechanical arm, the head may be placed within the tire so that testing using high voltage may be carried out.
Such pneumatic and/or mechanical arms for the placement of a head within the tire have a number of disadvantages. One disadvantage of such arms is expense. A complex arm that allows for precise placement of the head within the tire may be costly and may significantly affect the overall cost of the tire tester. In addition, such pneumatic and/or mechanical arms may require a large amount of time to properly place within the tire. There are, for example, a large variety of adjustments that may be made with such arms to properly adjust the head within the tire to be tested. A large number of different mechanical or pneumatic arms may also be necessary for different tire sizes. Finally, it may be difficult to achieve the proper placement of the head within the tire, which may affect the performance of the tire tester. The overall cost of prior art tire testing devices may also be high due to the large number of pieces of machinery required for use of such systems, such as a rotating apparatus for the tire and a spreader for the tire.
Because the mechanical or pneumatic arm used to place the head within the tire is typically mounted to a specific tire spreader, and because tire spreaders may come in a variety of designs, the mechanical or pneumatic arms commonly have to be built specifically for one tire spreader size and design. Prior art testing devices that use a mechanical or pneumatic arm to place the head within the tire are therefore specifically designed for a tire spreader and are therefore dependent on the configuration of the tire spreader. Such testing systems, in fact, typically are purchased along with a specific tire spreader, which results in an expensive tire tester.
A need exists for a tire testing device that has a cost efficient design, that allows a head carrying voltage to be properly placed and centered within a tire, and that may be placed within a tire and properly centered quickly and easily. A need also exists for a tire testing device that is independent of the configuration of the tire spreader and that may therefore be sold separately from a tire spreader, which reduces the price of the tire testing device.